Bazel client: SplitPath works with Windows paths

This allows correct behavior of Dirname and
Basename on Windows.

See https://github.com/bazelbuild/bazel/issues/2107

--
PiperOrigin-RevId: 142441234
MOS_MIGRATED_REVID=142441234

4 files changed, 66 insertions, 12 deletions

diff --git a/src/main/cpp/util/file.cc b/src/main/cpp/util/file.cc
index 2f6e6c66f2..392af372af 100644
--- a/src/main/cpp/util/file.cc
+++ b/src/main/cpp/util/file.cc
@@ -69,18 +69,6 @@ bool WriteFile(const std::string &content, const std::string &filename) {
   return WriteFile(content.c_str(), content.size(), filename);
 }
 
-pair<string, string> SplitPath(const string &path) {
-  size_t pos = path.rfind('/');
-
-  // Handle the case with no '/' in 'path'.
-  if (pos == string::npos) return std::make_pair("", path);
-
-  // Handle the case with a single leading '/' in 'path'.
-  if (pos == 0) return std::make_pair(string(path, 0, 1), string(path, 1));
-
-  return std::make_pair(string(path, 0, pos), string(path, pos + 1));
-}
-
 string Dirname(const string &path) {
   return SplitPath(path).first;
 }
diff --git a/src/main/cpp/util/file_platform.h b/src/main/cpp/util/file_platform.h
index 1db579a494..78322dfeb8 100644
--- a/src/main/cpp/util/file_platform.h
+++ b/src/main/cpp/util/file_platform.h
@@ -26,6 +26,9 @@ class IPipe;
 
 IPipe* CreatePipe();
 
+// Split a path to dirname and basename parts.
+std::pair<std::string, std::string> SplitPath(const std::string &path);
+
 // Replaces 'content' with contents of file 'filename'.
 // If `max_size` is positive, the method reads at most that many bytes;
 // otherwise the method reads the whole file.
diff --git a/src/main/cpp/util/file_posix.cc b/src/main/cpp/util/file_posix.cc
index e197a09453..9e835d759e 100644
--- a/src/main/cpp/util/file_posix.cc
+++ b/src/main/cpp/util/file_posix.cc
@@ -169,6 +169,18 @@ IPipe* CreatePipe() {
 }
 #endif  // __CYGWIN__
 
+pair<string, string> SplitPath(const string &path) {
+  size_t pos = path.rfind('/');
+
+  // Handle the case with no '/' in 'path'.
+  if (pos == string::npos) return std::make_pair("", path);
+
+  // Handle the case with a single leading '/' in 'path'.
+  if (pos == 0) return std::make_pair(string(path, 0, 1), string(path, 1));
+
+  return std::make_pair(string(path, 0, pos), string(path, pos + 1));
+}
+
 bool ReadFile(const string &filename, string *content, int max_size) {
   int fd = open(filename.c_str(), O_RDONLY);
   if (fd == -1) return false;
diff --git a/src/main/cpp/util/file_windows.cc b/src/main/cpp/util/file_windows.cc
index 29153d1812..1d00269002 100644
--- a/src/main/cpp/util/file_windows.cc
+++ b/src/main/cpp/util/file_windows.cc
@@ -21,6 +21,7 @@
 
 namespace blaze_util {
 
+using std::pair;
 using std::string;
 
 class WindowsPipe : public IPipe {
@@ -71,6 +72,56 @@ IPipe* CreatePipe() {
   return new WindowsPipe(read_handle, write_handle);
 }
 
+static bool IsRootDirectory(const string& path) {
+  // Return true if path is "/", "\", "c:/", "c:\", "\\?\c:\", or "\??\c:\".
+  //
+  // It is unclear whether the UNC prefix is just "\\?\" or is "\??\" also
+  // valid (in some cases it seems to be, though MSDN doesn't mention it).
+  return
+      // path is "/" or "\"
+      (path.size() == 1 && (path[0] == '/' || path[0] == '\\')) ||
+      // path is "c:/" or "c:\"
+      (path.size() == 3 && isalpha(path[0]) && path[1] == ':' &&
+       (path[2] == '/' || path[2] == '\\')) ||
+      // path is "\\?\c:\" or "\??\c:\"
+      (path.size() == 7 && path[0] == '\\' &&
+       (path[1] == '\\' || path[1] == '?') && path[2] == '?' &&
+       path[3] == '\\' && isalpha(path[4]) && path[5] == ':' &&
+       path[6] == '\\');
+}
+
+pair<string, string> SplitPath(const string& path) {
+  if (path.empty()) {
+    return std::make_pair("", "");
+  }
+
+  size_t pos = path.size() - 1;
+  for (auto it = path.crbegin(); it != path.crend(); ++it, --pos) {
+    if (*it == '/' || *it == '\\') {
+      if ((pos == 2 || pos == 6) && IsRootDirectory(path.substr(0, pos + 1))) {
+        // Windows path, top-level directory, e.g. "c:\foo",
+        // result is ("c:\", "foo").
+        // Or UNC path, top-level directory, e.g. "\\?\c:\foo"
+        // result is ("\\?\c:\", "foo").
+        return std::make_pair(
+            // Include the "/" or "\" in the drive specifier.
+            path.substr(0, pos + 1), path.substr(pos + 1));
+      } else {
+        // Unix path, or relative path.
+        return std::make_pair(
+            // If the only "/" is the leading one, then that shall be the first
+            // pair element, otherwise the substring up to the rightmost "/".
+            pos == 0 ? path.substr(0, 1) : path.substr(0, pos),
+            // If the rightmost "/" is the tail, then the second pair element
+            // should be empty.
+            pos == path.size() - 1 ? "" : path.substr(pos + 1));
+      }
+    }
+  }
+  // Handle the case with no '/' or '\' in `path`.
+  return std::make_pair("", path);
+}
+
 #ifdef COMPILER_MSVC
 bool ReadFile(const string& filename, string* content, int max_size) {
   // TODO(bazel-team): implement this.